Background: A tragedy of the commons arises if individuals cannot protect their future use of a depletable resource, and individual fitness increases if individuals exploit the resource at rates beyond sustainability. Natural selection then forces the individuals to diminish, perhaps even to destroy, their resource. One way to protect future use is privatization – that is, locally excluding rivals from the resource. Another is to reduce rivalry among individuals by restricting exploitation rates.

Questions: Under what conditions will natural selection increase excludability? If relatedness among individuals is high, will kin selection be enough to eliminate or weaken the evolution of privatization?

Mathematical method: We use a simple model that captures the tension between individual and group success. Then, we calculate the evolutionarily stable strategy using the standard optimization techniques of evolutionary game theory.

Conclusions: Selection for privatization occurs at low values of relatedness. The conditions for this to occur resemble those previously obtained for the reduction of rivalry because non-excludability of damage, and not rivalry per se, is the fundamental cause of the tragedy of the commons.

Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

All copies of abstracts and articles must preserve their copyright notice without modification.